Fusible link



Nov. 7, 1933.

G. l. RocKwooD ,934,279

FUSIBLE LINK Filed June 19, 1929 lll! 3.1. 30 17 32 MMYM Y Patented Nov. 7, 1933 FUSIBLE LINK George I. Rockwood,v l/Vorcester, Mass., assigner to Rockwood Sprinkler Company of Massachusetts, Worcester, Mass., a corporation of Massachusetts Application June 19, r1929. Serial No. 372,140

5 claims.

This invention relates to fusible links such as are commonly used for releasing heat-controlled apparatus, such as fire doors, sprinkler heads and other similar' devices. In such links, it is desirable to use a solder or fusible alloy having a very low melting point, commonly between 140 and 160 F. Such low-melting alloys commonly contain'bismuth and the very low alloys also contain mercury. It is found that such alloys are structurally weak and unreliable and that they are very poorly adapted to resist tension or shearing stresses.

1t is the general object of my invention to provide a fusible link in which such low-melting alloys may be satisfactorily and effectively used, regardless of their structural weakness.

A fiu'ther object is to provide a fusible link in which the fusible element is at all times under compression, a condition effectively sustained by even a weak alloy.

A further feature of the invention relates to the provision of a fusible link so constructed that the fusible element is entirely enclosed and protected from the atmosphere, and also so constructed that the link cannot be readily reassembled after a single release operation thereof.

My invention further relates to arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claims.

A preferred form of the invention is shown in the drawing in which Fig. 1 is a plan view of my improved link;

Fig. 2 is a side elevation thereof;

Fig. 3 is a plan view of one of the terminal members of the link;

Fig. e is a sectional elevation, taken along the line 4-4 in Fig. 3;

Fig. 5 is a plan view of a spacing member;

Fig. 6 is a sectional elevation, taken along the line 6 6 in Fig. 5;

Fig. 7 is a perspective view of the fusible element;

Fig. 8 is a plan view of the second terminal member;

Fig. 9 is a sectional elevation, taken alongthe line 9-9 in Fig. 8;

Figs. 10, 11 and 12 are sectional Views, partly in perspective, illustrating the manner in which the several parts of the fusible link are assembled; and

Fig. 13 is a sectional side elevation of the assembled link.

Referring to the drawing, my improved fusible link comprises terminal members l0 and 1l,

preferably having openings 12 therein to receive the ends of wire cables C or such other devices as may be attached thereto. The openings l2 are preferably reenforced about their peripheries in any convenient manner, as by expanding and beading overthe material struck out from the centers of the openings.

The details of construction of the terminal member l0 are shown in 3 the me1nber being provided with an 15 and side flanges 16 of slightly greater width but tapern ing toward the other end of said member. The member l0 is also provided with a rectangular opening 17 having an offset lip 18 along one side thereof.

The second Yterminal member ll is provided with a similar reenforced opening 12 in its outer end portion and the body portion 20 thereof is offset downwardly, as indicated in 9, and is provided with 11p-turned lugs or projections 22 at each side thereof and with a downwardly offset projection or lip 23, disposed between the lugs 22.

A spacing member 30 (Figs. 5 and 6) is made of such size as to fit between thefianges Y16 of* the member 10 and is provided with a flange 3l at one end and with a downwardly projecting lug 32 at the other end, the lug 32 being of less Width than the member 3G. The fusible element 35 (Fig. 7) is preferably in the form of an elongated rectangular bar of the desired lowmelting alloy.

Having described the details ofconstruction of the parts of my improved link, the method of assembling is best understood by reference to Figs. l() to 13 inclusive.

The spacing member 3l) is rst placed in the terminal member 10, with the lug 32 projecting downward into the rectangular opening 17. The fusible element 35 (Fig. 1l) is then inserted between the end flange 15 of the member 10 and the flange 31 of the spacing member 30. The offset portion 23 of the terminal member 11 is then inserted in the opening 17 beyond the spacing member 30, as indicated in Fig. 12.

The lugs 22 are then bent downward against the terminal member 10, as indicated by the arrow a (Fig. 12), and all of the joints between the two terminal members are then treated with the same low-melting solder, so as to effectively seal the fusible element 35 within the space enclosed by the terminal members and to fully protect all adjoining surfaces of the terminal ineinbers from atmospheric corrosion.

When the parts are assembled, as shown inV Fig. 13, it will be evident that the terminal members and 11 cannot be separated by a direct lengthwise tension so long as the fusible element is in position, as the offset projection 23 fis locked in the opening 1'7 and under the terminal member 10 by the spacing member 30.

When the melting temperature is encountered, however, the solder around the joints will be immediately liquefied and the fusible element 35 will also melt and will run out through the uncovered joints. As soon as this occurs, the spacing member 30 is free to slide to the left, as viewed in Fig. 13, thus permitting the lip 23 to be pulled upward through the opening 17, Whereupon the terminal members 10 and 11 completely separate and the heat-controlled apparatus is released.

The lugs 22 are not entirely necessary for satisfactory operation of the device, but are provided primarily to prevent reassembling of the link after a single release operation thereof. Such reassembling is undesirable, as it is commonly done by inexperienced persons and frequently the fusible element inserted is not of the proper melt- V Ving point.

With the lugs 22 bent downward, as indicated in Figs. 12 and 13, it is difficult to reassemble the parts unless the lugs are reversely bent back to their original positions.

Having thus described my invention, it will be `fseen that I have provided a fusible link in which the fusible element may be a very low-melting alloy, which is so positioned in the device that the structural weakness or unreliability of the metal is of no disadvantage to effective operation,

as the fusible element is under simple comelement being disposed between said terminal members and preventing relative movement of longitudinal separation thereof by any tension exerted on said members in a direction tending to separate said members longitudinally.

2. A fusible link comprising a pair of relatively slidable terminal members, and means to prevent longitudinal sliding movement thereof, said means including a fusible element held under compression in said link, and of elongated rectangular shape, with the extended side surfaces thereof compressively engaged.

3. A fusible link comprising relatively slidable members providing an enclosed recess, and a fusible element held under compression in said recess, one of said members having projecting portions preventing reassembly of said fusible link after a single release operation thereof.

4. A fusible link comprising a terminal member having an end iiange and a rectangular body opening, a second terminal member having an offset lip extending through said opening, a spacing member having a lug extending through said opening and an end fiange adjacent and parallel to said nrst mentioned flange, and a rectangular fusible element held under compression between` in said opening, a spacing member, and a fusible element held under compression between said spacing member and said end flange by any tension exerted on said link members in a direction tending to separate said members by relative longitudinal sliding movement, and said spacing member and fusible element preventing relative longitudinal sliding movements of said link members and preventing Withdrawal of said offset end portion from said transverse opening.

GEORGE I. ROCKWOOD. 

